It is known in the prior art to generate speed code signals to control the movement of a train vehicle, with the frequency of the provided speed control signal corresponding to a particular desired train vehicle speed of operation. For the purpose of controlling a train vehicle moving along a track including a plurality of signal blocks a series of frequency signals are needed for the respective desired train vehicle speeds, and which signals are failsafe and cannot change without detection of such change. For example, a 30 mph speed command signal cannot drift by itself to a 40 mph signal because that would be unsafe. Thusly, there is a need for generating a predetermined frequency signal for many applications, which frequency cannot change. These speed control signals may be F1 for providing a 10 mph speed for a train vehicle in a given signal block, F2 for providing a 20 mph train vehicle speed, F3 for providing a 30 mph train vehicle speed, and so forth, up to the maximum desired speed for the train vehicle.
It is known in the prior art to control the speed of a train vehicle using a master oscillator providing an output signal at a frequency of 1 megacycle, and a first associated frequency divider to provide an output signal having a frequency of 2 KHz. for controlling the speed of a train vehicle in a signal block at 10 mph, a second associated frequency divider provides an output of 3 KHz. for 20 mph train vehicle operation, a third associated frequency divider provides an output speed signal of 4 KHz. for controlling the train vehicle speed at 30 mph, a fourth associated frequency divider provides an output signal of 5 KHz. for controlling the train vehicle speed at 40 mph, and a fifth associated frequency divider provides an output signal of 6 KHz. for controlling the train vehicle speed at a maximum speed of 50 mph, and so forth. The absence of a frequency signal would be a speed command of 0 mph.
It is known to control the movement speed of a train vehicle along a track including a plurality of signal blocks through the use of speed code signals in accordance with failsafe control system operation. Attention is called to U.S. Pat. No. 3,562,712 of G. M. Thorne-Booth et al, U.S. Pat. No. 3,551,889 of C. S. Miller and U.S. Pat. Nos. 3,532,877 and re-issue 27,472 of G. M. Thorne-Booth for prior art disclosures of similar railway track signalling systems. In addition, an article entitled, "Design Techniques For Automatic Train Control" by R. C. Hoyler in the Westinghouse Engineer for July, 1972 at pages 98 to 104 and an article entitled "Automatic Train Control Concepts Are Implemented By Modern Equipment" by R. C. Hoyler in the Westinghouse Engineer for September, 1972 at pages 145 to 151 describe train control equipment designed for safe operation.
It is known in the prior art to utilize an electrical signal supply arrangement including two self-sustaining oscillator generators, either one of which is adapted to supply the output speed code signal upon failure of the other, as shown by U.S. Pat. No. 3,047,816 of Drake et al.